Tom Watson, a former defence minister and deputy
chairman of the Labour Party, said there was an urgent need for “public
scrutiny” of the activities at RAF Croughton, a US Air Force base in
Northamptonshire which is a major hub for American military and clandestine
communications.

The Independent
revealed this week that the base is used to route vast amounts of data
captured by Washington’s “Stateroom” network of listening posts in
diplomatic premises back to America for analysis by the CIA and the National
Security Agency.

The network is at the centre of revelations that the NSA
intercepted a mobile phone used by Mrs Merkel. A spying “nest” on the roof
Washington’s Berlin embassy appears to have been abruptly turned off last
week following an incendiary row between Germany and America about the
eavesdropping.

Documents provided by NSA whistleblower Edward Snowden imply that
any material gathered from the Berlin embassy listening post would have been
relayed back to a joint CIA/NSA facility in Maryland via a secure link
within RAF Croughton.

In a letter copied to members of Parliament’s Intelligence and
Security Committee ahead of Thursday’s appearance by the heads of Britain’s
three main spying agencies, Mr Watson said The Independent’s revelations
added to existing concerns that RAF Croughton is used as a support site for
US drone strikes in Yemen.

The MP said: “The use of RAF Croughton by the NSA, CIA and other US
officials puts our country at real risk of complicity in both unlawful
eavesdropping and the unlawful killing of civilians overseas by the US.
These allegations also undermine our relations with other key allies.

“The time has come for the use to which RAF Croughton is put to be
subject to public scrutiny - proper investigation is needed.”

Mr Watson asked Mr Hague to make a statement to the House of
Commons outlining Government policy regarding the apparent use of RAF
Croughton and other US-manned bases to assist Washington’s embassy-based
listening operation, which is run in parallel with a similar British network
run by GCHQ.

He also asked for the matter to be raised with US Secretary of
State John Kerry.

An FCO spokesperson said: “In line with long-standing practice we
do not comment on intelligence matters."